diff --git a/include/picotls.h b/include/picotls.h
index 1382499..1be5fd2 100644
--- a/include/picotls.h
+++ b/include/picotls.h
@@ -931,7 +931,7 @@
                  */
                 ptls_iovec_t configs;
                 /**
-                 * slot to save config obtained from server upon config mismatch
+                 * slot to save the config obtained from server on mismatch; user must free the returned blob by calling `free`
                  */
                 ptls_iovec_t *retry_configs;
             } ech;